Flexible couplings are already known between two lengths of tube in which a gas flows. In particular, U.S. Pat. No. 4,427,220 describes a flexible coupling comprising a first and a second length of exhaust pipe, in which the first length of exhaust pipe comprises a pivot portion in the form of a spherical ring projecting outwardly from a cylindrical outside surface portion of the first length of exhaust pipe, an annular exhaust gasket pressing against an inside surface of the pivot portion, an anti-friction member pressed against an outside surface of the pivot portion, and a housing carried by the inside of the second length of the exhaust pipe and pressing both the annular gasket and the anti-friction member against the pivot portion.
The structure of the housing in this coupling is extremely complex and completely incompatible with the cost constraints applicable in various fields, and in particular in the field of exhaust pipes for motor cars. Further, because the housing is disposed inside the second length of tube, the housing is directly subjected to the gases flowing along the lengths of tube. This structure is thus incompatible with the coupling being used on lengths of exhaust pipe from car engines having very high exhaust gas temperatures.
An object of the present invention is to provide a flexible exhaust coupling of simple structure, which is easy to make, cheap, and which nevertheless provides good sealing between the lengths of the exhaust pipe.